Affection = gentle lasting love like that of a parent for child.

• He has a deep affection for his old friends.
• She doesn’t show any affection for him.
• They showed a great amount of affection and gratitude for a small favour done by us.
• An affectionate hug/child.

Affectation = behaviour which is not one’s natural manner.

• She is sincere and quite without affectation.
• I wore sunglasses and people thought it was an affectation.
• The way she speaks reeks of affectation.

Affected = (adjective) pretended, not real, insincere.

• He spoke with an affected English accent.
• She had an affected smile on her face.
• He spoke in an affected manner.

Affect =(verb) influence, to cause some result or change in.

• Smoking affects health.
• The strike of mine-workers affected the price of coal.
• The government policy of the new taxation will affect the business community.